M&S says

The perfect dinner party plate, this simple yet chic porcelain side plate is a bright white for a modern and simple style. This side plate adds understated sophistication to any occasion, perfect for bread, cakes or finger food, and is finished with our unique StayNEW™ technology, meaning it retains its colour for longer. This side dish is perfect for busy modern kitchens too as it is safe to use both in the dishwasher and microwave.